High Lockout
F.00 on Vaillant Turbomax Plus 828

Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit due to a sensor or wiring fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Flow-NTC: NTC broken; NTC cable broken; Defective connection at NTC Defective connection at electronics | Flow-NTC cable defective/ broken NTC faulty

What causes this fault?

This fault occurs when the boiler's main control board loses communication with the temperature sensor that monitors the water leaving the unit. The most common reason is that the sensor itself has failed due to age or internal wear, though it can also be caused by loose wiring or water damage to the electrical connections inside the casing.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.01View →F.10View →F.11View →

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